1. Field of the Invention
The invention relates to a method for the manufacture of a shaft seal assembly which includes an elastomeric static gasket and a plastic shaft seal lip each bonded to a casting with the elastomeric gasket material securing the plastic seal lip to the casting. The seal assembly is particularly adapted for use in sealing a crankshaft casing.
2. Description of the Prior Developments
In a known seal of this type (EP-A-139,503) firstly the shaft seal ring is shaped onto the radial flange of a cross-sectionally L-shaped sheet metal ring. For connection to a gasket receptacle, the outer, axially parallel portion of the ring is inserted in the cavity of an injection mould, so that in the case of the finished seal the outer portion of the sheet metal ring is received in a recess, in the form of an inner groove, of the gasket receptacle in the form of a plastic moulding the ring is fastened to the receptacle on both sides by elastomer material, which is also used for the static gasket and is linked therewith. The thus formed gasket module comprising the gasket receptacle with the shaft seal ring and the static gasket leads to a prefabricated, interchangeable unit. The described fastening by the axially parallel portion of the L-shaped sheet metal ring requires the shaping of the plastic gasket receptacle on the sheet metal ring, either before or after shaping the shaft seal ring on the inner portion of the sheet metal ring. The elastomer material injected on either side of the axially parallel portion ensures an elastic fastening. As a result of this design type the necessary limited radial tolerances for obtaining the coaxial nature of the sealing lip to the shaft are not always respected. Problems are also caused by the settling or creep of the plastic moulding under screw force, which can lead to leaks between the crankcase and the seal.
For the main use of the invention of the driven side crankshaft seal in motor vehicles, in which the crankshaft, the end wall of the crankcase and the crankcase wall perpendicular thereto are to be sealed with respect to the oil pan or sump, a seal with a light metal pressure die casting as the gasket receptacle has proven completely satisfactory. For the assembly of such a seal all the parts, namely the radial shaft seal ring, the pressure die casting, a flat gasket serving as a static gasket over the end wall of the crankcase, etc. are individually made available, which requires numerous working steps during assembly. This multipart solution leads to many error possibilities and in particular the possibility of damaging the individual components of the shaft seal. In this connection tests carried out by the applicant have revealed that shaft seals often have to be disposed of as waste due to damage in the sealing edge area of the shaft seal ring.